1. Field of the Invention
This invention relates to a rectangular substrate dry etching apparatus for etching a rectangular substrate of a large size principally for use with a field emission display or a liquid crystal display.
2. Description of the Prior Art
When a rectangular substrate of a large size for use with a field emission display or a liquid crystal display is to be worked finely by dry etching, a dry etching apparatus for the fabrication of ordinary semiconductor devices having a large etching chamber is employed.
As such dry etching apparatus, an ordinary plasma etching apparatus of the parallel flat plate type, a magnetron plasma etching apparatus, an electronic cyclotron resonance (hereinafter referred to briefly as ECR) plasma etching apparatus or the like is employed.
Also a distribution ECR (hereinafter referred to briefly as DECR) plasma etching apparatus is employed frequently. General structure of an exemplary one of conventional DECR plasma etching apparatus is schematically shown in FIGS. 4 and 5. Referring to FIGS. 4 and 5, microwaves of a frequency of 2.45 GHz generated by a magnetron oscillator 51 are transmitted by way of a waveguide 52 to a splitter 53, at which they are distributed into a plurality of coaxial cables 54. The microwaves thus distributed propagate along the coaxial cables 54 and are radiated from a plurality of bar-like antennae 56 disposed along an inner side wall of an etching chamber 55. High density plasma 63 is generated at a position spaced from a rectangular substrate 74 by the microwaves 61 radiated from the bar-like antennae 56 and a magnetic field 62 (magnetic flux density of 875 Gauss) satisfying an ECR requirement. The rectangular substrate 74 is etched with diffusion plasma 64 consisting of diffusion components of the high density plasma 63.
With a plasma etching apparatus of the parallel flat plate type, however, a rectangular substrate to be worked is liable to be damaged. If the bias current to be applied to a rectangular substrate is decreased in order to reduce damage, the etching rate is reduced and the etching uniformity is deteriorated.
Meanwhile, with an ECR plasma etching apparatus, it is difficult to generate plasma of a large diameter uniformly such that it completely covers a rectangular substrate. Consequently, the etching uniformity is low.
On the other hand, with such a DECR plasma etching apparatus as described above, a sufficiently high microwave power cannot be propagated because microwaves distributed by a splitter are propagated to antennae by way of coaxial cables. Consequently, the etching rate is low and much time is required for etching. If the size of the rectangular substrate increases, then the etching rate decreases as much.
Accordingly, whichever one of such conventional dry etching apparatus is used, it is difficult to etch a rectangular substrate of a large size with a high degree of accuracy.